Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hello All, I am sending this e-mail to the list to ask for food for thoughts. I have two same servers based on AMD x2 64bit loaded with CENTOS5. Memory and resources are not a problem since I begun with small systems and can expand up to 8 SATA disks, 2 IDE, 16GB RAM. Now I have the same setup for HDs on both of them. One 80Gbyte and one 320Gbyte both IDE and sharing the /boot and / in RAID-1. Also the left over space on both of them will be used as DRBD devices (that is /dev/hda4 --> /dev/drbd0 and /dev/hdb4 --> /dev/drbd1) in primary/primary config. What I plan to have as active applications are: 1. ORACLE 2. MySQL Production 3. MySQL Development 4. Apache 5. storage for documents 6. and in the future compilation and execution of MPI based code I have thought about the possible implementation and I end up with two scenarios. FIRST: /dev/drbd0 and /dev/drbd1 are members of one physical volume. Then running cman, gfs2 and clvmd, I create on large logical volume out of them, and then I format it as GFS2. All the disk space is simultaneously available and mounted as GFS on both servers. I create the directories with proper permissions that the applications will use. Using system-config-cluster or COGNA, I configure the services I want, and "run" them on the nodes I select. It looks that this scenario gives me the good option of live backup on either node (since the whole FS is mounted at the same time to both nodes), simple application migration if a node fails and easy expansion of the file system (I add on the PV the new /dev/drbd when I add a new disk and then expand gfs2). That way I keep a coherent image of my files and at the same time I can keep on adding disks, applications or whatever easily. Now it seems to me that the problem with this setup, is how to make exploitation of the cluster manager (RHEL 5), in a way that will auto migrate the applications if the DRBD fails on one node. Is there any way to exploit the CMAN instead of heartbeat to manage first of all the underneath DRBD devices? And then how will cman be aware that it must not start the application because the FS could not be mounted? Maybe use a custom script as resource? SECOND: Again /dev/drbdX are members of the same physical volume. However this time, I create separate LVs formatted with ext3, one for every application that will run. Then with CMAN I create as resource also the LV to be mounted prior to the start of the service that is using it. In this it looks like the question of the previous scenario, on how I will control via CMAN the DRBD devices is some how solved. If it can not mount the LV this means that there is a problem with DRBD. But in that case the service is related to prior mounting the respective LV so it will not start. However I think that this does not scale well and also it looks like I will have an issue with backup. For backup I will use an external USB disk connect to one of the server, via which the already mounted FSs will be backed up! I appreciate your comments and sharing your experiences. Sincerely, Theophanis Kontogiannis -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20080312/09c9cc92/attachment.htm>